Inductive transmitter



March 1960 A. KRUSSMANN 2, 2 60 INDUCTIVE TRANSMITTER Filed Feb. 19,1957 INVENTOR.

1461 0] K7 5 m W United States Patent mnucrrvn TRANSMITTER AdolfKriissmann, Minden, Westphalia, Germany, assignor to Schoppe & Faeser,G.m.b.H., Minden, Westphalia, Germany Application February 19, 1957,Serial No. 641,084

7 Claims. (Cl. 336-132) The present invention relates to inductivetransmitters, such as are used for developing an electrical voltagesignal of amplitude corresponding to the sensed magnitude of acondition.

A primary object of the invention is provision'of a device of the kindin question of novel arrangement productive of superior operatingcharacteristics and practical utility as compared to the conventionalarrangements heretofore used for similar purposes, such as transformerswith relatively rotatable primary and secondary windings or whereinrelatively fixed primary and secondary wiud ings are variably coupled bya movable core piece.

The present invention is based on the primary concept of a transformerwherein the primary and secondary windings respectively are magneticallycoupled to different core structures each of which has a pair of endsurfaces as distinguished from endless or ring cores, and wherein an endsurface of one core structure is movable along the surface of the otherwinding, in the directions of longitudinal extent of the core that iscoupled to the latter winding, thereby varying the inductiveintercoupling of the different electrical circuits provided by the twowindings, and correspondingly varying amplitude of voltage induced inthe secondary one of the windings. The invention also embraces a type ofarrangement providing magnetic coupling between the two magnetic cir-'cuits that is highly and substantially uniformly efficient throughoutthe full range of relative movement of the two core structures.

As compared to the mentioned conventional devices of the prior art thepresent invention very materially increases ranges of relative movementwherein variation of output voltage is linearly responsive to movementsof the adjustable control member. As hereinafter disclosed, theinvention may be embodied in a rotary form ofdevice, thereby avoidingthe restriction to linear motion encountered in movable coretransformers, and the movable member of the disclosed device is operablethroughout almost three hundred sixty angular degrees, withsubstantially linear response throughout the full movement range,thereby eliminating the restriction encountered in rotatabletransformers to practical ranges of ninety or fewer angular degrees ofpositional adjustment of the relatively movable parts.

In the accompanying drawings:

Fig. 1 is a perspective view of the working parts of an assemblyembodying the invention.

Fig. 2 is a schematic perspective showing the electrical and magneticcircuits of the device of Fig. 1.

Fig. 3 is an elevation, partly in median section of a complete unitembodying the invention and also in the specific arrangement of Figs. 1and 2.

In the illustrated arrangement, the device comprises a first magneticcircuit provided by a first core 6 of high magnetic permeability,provided with a gap 7 and longitudinally formed annular. An electricallyconductive winding 8 is magnetically coupled to core 6, preferably bythe illustrated encirclement of the core by the turns of ice] PatentedMar. 8, 1960 the winding, and the turns are distributed along core 6.For a linear response characteristic distribution of the turns ofwinding 8 is uniform and symmetrical relative to gap 7.

A second magnetic circuit is provided by a highly magnetically permeablecore structure 9 that is provided with an end surface 1% positioned infacing adjacency to a lateral surface of winding 8, and that, bymovement of structure 9, is adjustable along that lateral surface in thedirections of longitudinal extent of core 6 and winding 8, so that armportions of the electromagnetic circuit structure provided by core 6 andwinding 8, which arm portions are defined by and lie respectivelybetween opposite sides of core structure end surface 10, and gap 7, andeach of which is returned to surface 10 through structure 9 as willappear, can be relatively and inversely varied by movement of surface10.

To provide for adjusting movement of surface 10, core structure 9comprises a rotatable shaft 11, a radial arm 12 projecting from thatshaft toward winding 8 and the end of which constitutes surface it and aplate 13 a marginal portion of which is positioned laterally of core 6for magnetic coupling therewith, as indicated by the arrows 14 of Fig.2. Preferably plate 13 is spaced from one side of winding 8 and thesecond electrical winding 15 is located between plate 13 and the spaceoccupied by electromagnetic circuit structure 6, S and arm 12, and inencircling relation to shaft 11. Plate 13 is of highly magneticallypermeable material and is provided with bearing means 16 wherein shaft11 is rotatable and closely engaged to minimize reluctance between itand the plate.

For linear response, facing surfaces of winding 8 and plate 13 should beparallel and spaced at a sufiicient distance to insure uniform fielddistribution along the space between, and winding 8 and plate 13 shouldbe parallel. For such purpose core 6 and the turns of winding 8 arepreferably of the indicated rectangular sections with the facingsurfaces of winding 8 and plate 13 disposed in parallel planes. Also forlinear response shaft 11 should be concentric with the annulus formed bystructure 6, 8, and for accuracy arm 12 preferably is of rectangularcross section substantially matching that of core 6 and with end surface10 registered with the inner side thereof. It will be seen thatnon-linear response, if required, may be provided by varying one or moreof such factors as distribution of turns of winding Salong core 6,positional relationship of axis of rotation of shaft 11 to axis of theannulus defined bystructure 6, 8, .and spacings of various surfaceportions of plate 13 from corresponding facing surfaceportions ofwinding 8.

It will be seen that while surface 10 is so positioned that the arms ofthe magnetic circuit provided by structure 8, 9 and which respectivelylie to opposite sides of surface 10, are symmetric, and with eitherwinding 8 or winding 15 energized by alternating current, as a primarywinding, equal and opposite magnetic forces will be developed in themagnetic paths respectively provided by the parts of core 6 lying toopposite sides of surface 10, extended across the space to plate 13 andthence through the common path arm provided by shaft 11 and arm 12.Consequently in that condition no voltage will be developed across theone of the windings that serves as the secondary. Upon upset ofcircuit-arm symmetry by displacement of surface 10, the oppositemagnetic forces will become unbalanced and a resultant voltage willappear across the secondary winding. It is contemplated that winding 15be used as the primary winding so that the secondary winding 8effectively is divided, by surface 10, into secondary winding sectionswherein opposed voltages are induced.

As shown in Fig. 3, a complete unit assembly may be arranged byproviding a low permeability housing portion including an end plate 18covering the end of the working assembly opposite plate 13, and acylindrical sidewall 19 that surrounds structure 6, 8 and winding 15 andthat is joined to the margin of plate 13. A low permeability plate 29may be interposed between the assembly of arm 12 and structure 6, 8, andwinding 8. To reduce eddy current losses shaft 11, plates 13 and 20 andhousing elements 13, 19 may all be provided with slots 21.

From the foregoing, the concept of the invention, and its utility, andmany advantages will be apparent as will be the possibilities of makingmany modifications, alterations and changes in the purely exemplaryspecific structural arrangement disclosed. Consequently it will beappreciated that the invention and its limits are defined and are to beascertained solely by and from the appended claims.

I claim:

1. An inductive transmitter assembly comprising an elongate core ofmagnetically permeable material longitudinally formed to surround aspace and provided with a gap, 21 first electrically conductive windingwhereof the turns encircle said core and are distributed along it, asecond core of magnetically permeable material located in the spaceenclosed by the first said core and spaced from said gap, and a secondelectrically conductive winding magnetically coupled with said secondcore, and magnetically permeable means extending to adjacent said secondcore from points on opposite sides of said gap and adjacent saidelongate core.

2. An inductive transmitter assembly comprising a first electromagneticcircuit including an elongate core of magnetically permeable materiallongitudinally formed to enclose a space and provided with a gap, and anelectrically conductive winding whereof the turns encircle said core andare distributed along it, and a second electromagnetic circuit includinga first core piece of magnetically permeable material located in andextended axially of said space, a second core piece of magneticallypermeable material attached to said first core piece and spaced fromsaid gap, said second core piece, projecting radially from the firstcore piece and having a terminal surface located adjacent said elongatecore, a second electrically conductive winding encircling one of saidcore pieces, and magnetically permeable means peripherally coextensivewith said elongate core providing a flux path between said elongate coreand said first core piece.

3. An inductive transmitter assembly comprising an annular firstelectromagnetic circuit structure including a magnetically permeableannular core having a gap and an electrical winding whereof the turnsencircle and are distributed along said core, and a secondelectromagnetic circuit comprising magnetically permeable core meansincluding a support portion disposed within said core, an arm attachedto and extended radially from said support portion toward said core andhaving an end adjacent the turns of said winding, and a plate extendingfrom said support portion and projecting therefrom into adjacency to aside of said annular circuit structure to provide a flux path betweensaid first circuit structure and said support portion, and a secondelectrical winding encircling said support portion.

4. An inductive transmitter assembly according to claim 3, wherein saidannular circuit structure has a side extended substantially along aplane, said second winding is mounted outwardly of said plane, and saidplate is 7 located to the opposite side of said second winding from saidplane.

5. An inductive transmitter assembly according to claim 3, wherein saidplate is provided with bearing means rotatably penetrated by saidsupport portion, and including a casing member of material of lowmagnetic permeability surrounding said annular circuit structure and armand having a wall outwardly encircling the latter and attached to saidplate.

6. An inductive transmitter assembly comprising a magnetically permeableannular core of rectangular cross section and having a transverse gap, afirst electrical winding whereof the turns encircle and are distributedalong said core, a rotatable magnetically permeable shaft concentricwith said core, a radial arm of rectangular cross section attached tosaid shaft within and projecting into adjacency to inner surfaces ofsaid winding turns, a casing of material of relatively low magneticpermeability enclosing said core winding and arm and including a spacedpair of walls respectively overlying the opposite sides of said windingand at least one of which is rotatably penetrated by said shaft, and acircular side wall surrounding the periphery of said winding and havinga skirt portion projecting beyond one of said opposite sides, a secondelectrical winding located within said skirt portion, and outwardly ofthe adjacent one of said pair of walls and encircling said shaft, and aplate of magnetically permeable material located to the opposite side ofsaid second winding and having a marginal portion that contacts saidskirt portion, said plate being provided with bearing means rotatablypenetrated by said shaft.

7. An inductive assembly according to claim 3, where in said plate isprovided with a slot extending radially from said first portion and inalignment with said gap of the annular core.

References Cited in the file of this patent UNITED STATES PATENTS1,596,505 Moore Aug. 17, 1926 2,414,688 Chambers Jan. 21, 1947 2,507,763Caine May 16, 1950 FOREIGN PATENTS 302,923 Great Britain Dec. 20, 1928

